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Theoretical calculation of the steric effects of ortho substituents by the AM1 method

โœ Scribed by Tomoko Sotomatsu; Yoshiyuki Murata; Toshio Fujita

Publisher
John Wiley and Sons
Year
1991
Tongue
English
Weight
408 KB
Volume
12
Category
Article
ISSN
0192-8651

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โœฆ Synopsis

The AM1 calculation was done for ortho-substituted toluenes (0-X-C,H,-CH,) and ortho-substituted tertbutylbenzenes (o-X-C&-t-Bu). The difference in the calculated heat of formation between o-X-C,H,-CH, and o-X-CJI,-t-Bu was used as a theoretical steric index for ortho-X. The correlation of this theoretical steric index with the empirical steric parameter sets such as our recently defined E,(AMD) and the Taf-Kutter-Hansch (TKH) E, was examined. In spite of the simplicity of the model system, the theoretical index was linear with the E,(AMD) constant with a correlation coefficient of r = 0.972 for 17 substituents of various structures. Including the phenyl group, the correlation with the TKH E, constant was r = 0.948. The theoretically calculated index was shown to serve as a measure of the ortho steric effect.

Abstracted in part from the Ph.D. Thesis of T. Sotomatsu, Kyoto

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